In the prior art disclosed in JP-A-2002-44887, a rotor is constructed by embedding Nd—Fe—B sintered magnets in a rotor core. The magnets are each in the form of a flat linear plate in a plan view and are arranged such that they are substantially inscribed in an outer circumference of the rotor so as to provide an almost polygonal shape. Further, the magnets are arranged over the whole circumferential of the rotor, and magnetic poles are each constituted by a plurality of magnets grouped in the same number.
In the prior art described above, however, because the magnets are regularly arranged over the whole circumference of the rotor core such that they are inscribed in an outer circumferential circle of the rotor core, the magnetic flux distribution is dispersed to a large extent, and a satisfactory magnetic flux distribution cannot be obtained. Also, the distortion factor of the induced electromotive force waveform is large and the fundamental wave effective value of the induced electromotive force is reduced, whereby the efficiency of a rotating electric machine is deteriorated. Further, the cogging torque is enlarged and the startup current is increased when the rotating electric machine is operated as a motor. It is hence difficult to start the operation in a smooth way. In addition, because the permanent magnets are arranged over the whole circumference of the rotor, the number of magnets used is increased and the cost is pushed up.
With the view of overcoming the disadvantages set forth above, it is an object of the present invention to provide a permanent magnet rotating electric machine which has high efficiency and high performance, and is inexpensive.